Journalists, contractors, diplomats and members of the public were still required to be screened, as well as anyone entering through the building's main entrance.

Under the plan, approved by Parliament's presiding officers, those exempted from metal detector checks would be subject to random screening.

Department secretary Carol Mills said last week some security staff would be redeployed to other parts of the 4700-room, 32-hectare site during the trial.

After three days, security guards have begun distributing contact details for the department's customer service staff and are reportedly encouraging those facing longer wait times to complain.

Complaints have been met with generic emails referring individuals back to the DPS customer service team.

Press gallery journalists used social media to criticise the changes, with some labelling it dumb and ill-advised.

West Australian reporter Nick Butterly said press gallery journalists, who had permanent authorisation to work in the building, should have been exempted from daily security checks.

"Congrats to DPS for their mind-blowing stupid policy drop to x-rays for everybody except reporters entering Parliament House," he tweeted, followed by: "Obviously concerned someone from the Fin Review might go nuts with a Glock."

ABC News federal political reporter Simon Cullen said more security staff appeared to be monitoring the new system, which had caused slower entry times for those being scanned.

Fairfax Radio political reporter Frank Keany also used Twitter to vent frustration with the plan. "I asked security how the new system was going - 'Like clockwork', dripping with sarcasm," he wrote.

Australian National University security expert John Blaxland questioned the changes and said they could have been put in place as part of cost-cutting measures.

"There are resource implications but it does beg the question whether it is resource-driven, or indeed security-driven," Dr Blaxland said.

"I am presuming they have sought advice from ASIO on the security situation on this, and if they haven't sought that advice then they've got rocks in their heads."

He agreed Parliament House should have strict security in place. "Where is the security threat assessment that advised that this is OK?" he said.

A Department of Parliamentary Services spokeswoman said there were no major delays.

The spokeswoman confirmed all relevant Commonwealth agencies had provided advice during a recent review and that exemptions applied to elected member and staff, with a minimum background and criminal history check.

Many exempted individuals hold higher level security clearances.

Guards were visually identifying staff as they scanned photo ID.

Last week Ms Mills said the building had tougher security protocols than other Australian parliamentary buildings and the trial could be abandoned if there was an incident or special event.

A review of the trial was expected early next year.

In 2012, a 35-year-old Russian national disturbed a press conference by former prime minister Julia Gillard after gaining access through an unmanned door.

He spent about 20 minutes walking through the building's corridors and was escorted away after handing Ms Gillard a document outlining his views on terrorism and international security.

An Australian Federal Police investigation was launched into the incident.